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1.
In this study, the polyacrylonitrile (PAN)-based precursor was produced by electrospinning for the fabrication of oxidized
nanofiber nonwovens. The parameters adopted for the oxidation process were chosen from the thermal analysis results obtained
using DSC and TGA. The oxidation temperatures of 270, 300, and 330 oC were selected for heating times of 30, 50, and 70 min
at three levels of tension. The variations in yield rate, breaking strength, shrinkage and stiffness of the oxidized PAN-based
electrospun nonwovens were examined in this article. The results indicate that the physical properties of electrospun nonwovens
were affected by the oxidation conditions. In addition, the limit oxygen index (LOI) was found to increase with increasing heat treatment temperature and time. In addition, the optimum oxidation condition
was found to be heating temperature of 300 °C for a duration of 70 min. Under this condition, high-quality PAN-based oxidized
electrospun nonwovens were produced with aromatization index (AI) of 62 % and LOI of 44 %. 相似文献
2.
Ching-Iuan Su Yao-Xian Huang Jhih-Wei Wong Ching-Hsiang Lu Chih-Ming Wang 《Fibers and Polymers》2012,13(4):436-442
This study takes polyacrylonitrile (PAN) as a raw material for PAN-based nanofiber nonwoven prepared using electrospinning. First we construct a thermal-stable process for the fabrication of oxidized nanofiber nonwovens as the precursor. A semi-open high-temperature erect furnace is then used with steam as the activator, through carbonization and activation processes to prepare carbon nanofiber absorbents continuously. The experiment varies the production rate and activator flow rate to prepare carbon nanofiber absorbents. Experimental results show that carbon nanofiber adsorbents are primarily made up of micropores and mesopores, averaging under 20 Å. Given a production rate of 10–20 cm/min with a matching activator feed rate of 120 ml/min, the specific surface area can reach about 1000 m2/g, producing an adsorption ratio of carbon tetrachloride over 200 %. 相似文献
3.
Hany S. Abdo Khalil Abdelrazek Khalil Salem S. Al-Deyab Hamoud Altaleb El-Sayed M. Sherif 《Fibers and Polymers》2013,14(12):1985-1992
Silver nanoparticles imbedded in polyacrylonitrile (PAN) nanofibers and converted into carbon nanofibers by calcination was obtained in a simple three-step process. The first step involves conversion of silver ions to metallic silver nanoparticles, through reduction of silver nitrate with dilute solution of PAN. The second step involves electrospinning of viscous PAN solution containing silver nanoparticles, thus obtaining PAN nanofibers containing silver nanoparticles. The third step was converting PAN/Ag composites into carbon nanofibers containing silver nanoparticles. Scanning electron microscopy (SEM) revealed that the diameter of the nanofibers ranged between 200 and 800 nm. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) showed silver nanoparticles dispersed on the surface of the carbon nanofibers. The obtained fiber was fully characterized by measuring and comparing the FTIR spectra and thermogravimetric analysis (TGA) diagrams of PAN nanofiber with and without imbedded silver nanoparticles, in order to show the effect of silver nanoparticles on the electrospun fiber properties. The obtained carbon/Ag composites were tested as gram-class-independent antibacterial agent. The electrosorption of different salt solutions with the fabricated carbon/Ag composite film electrodes was studied. 相似文献
4.
Jianxin He Yuman Zhou Kun Qi Lidan Wang Pingping Li Shizhong Cui 《Fibers and Polymers》2013,14(11):1857-1863
In order to fabricate continuously twisted nanofiber yarns, double conjugate electrospinning had been developed using two pairs of oppositely charged electrospinning nozzles. The principle and process of this novel yarn spinning method were analyzed, and the effect of applied voltage, nozzle distance between positive and negative, solution flow rate and funnel rotating speed on the diameters, twist level and mechanical properties of resultant PAN nanofiber yarns were investigated in this paper. The results indicated that electrospun nanofibers aggregated stably and bundled continuously at the applied voltage of 18 kV, the nozzle distance of 17.5 cm between positive and negative, the overall flow rate of 3.2 ml/h and the flow ratio of 5/3 for positive and negative nozzles. The resultant nanofiber yarns had favorable orientation and uniform twist distribution, and the twist level of nanofiber yarns increased with the increase of the ratio of funnel rotating speed and winding speed. The diameters and mechanical properties of nanofiber yarns depended on their twist level. The diameters of prepared PAN nanofiber yarns ranged from 50 µm to 200 µm, and the strength and elongation of PAN nanofiber yarns at break were 55.70 MPa and 41.31%, respectively, at the twist angle of 41.8 °. This method can be also used to produce multifunctional composite yarns with two or more components. 相似文献
5.
Electrospinning is an efficient method to produce polymer fibers with a diameter range from nanometers to a few microns using
an electrically driven jet. Electrospun nanofiber nonwoven fabrics can be applied into different areas with higher air volume
fraction, especially applied into textile materials with good warmth retention property. In this article, the air volume fraction
in nonwoven mats made of electrospun nanofibers was verified by studying fiber volume fraction in the mats. Then the relationship
between fiber volume fraction and fiber diameter was derived, and the fiber volume fraction is in direct ratio to the square
of fiber radius. By experimental verification, to get electrospun PAN nanofiber nonwoven mats with high air volume fraction
about 99 %, it can fix the polymer concentration on 8 %. The voltage fixed on 20 kV, the tip-to-collector distance on 15 cm.
The experiment is in accordance with the theory excellently. 相似文献
6.
Layered fabric systems with electrospun polyurethane fiber web layered on spunbonded nonwoven were developed to examine the
feasibility of developing protective textile materials as barriers to liquid penetration using electrospinning. Barrier performance
was evaluated for layered fabric systems, using pesticide mixtures that represent a range of surface tension and viscosity.
Air permeability and water vapor transmission were assessed as indications of thermal comfort performance. Protection performance
and air/moisture vapor transport properties were compared for layered fabric systems and existing materials for personal protective
equipment (PPE). Layered fabric systems with electrospun nanofiber web showed barrier performance in the range between microporous
materials and nonwovens used for protective clothing. Layered fabric structures with the web area density of 1.0 and 2.0 g/m2 exhibited air permeability higher than most PPE materials currently in use; moisture vapor transport was in a range comparable
to nonwovens and typical woven work clothing fabrics. Comparisons of layered fabric systems and currently available PPE materials
indicate that barrier/transport properties that may not be attainable with existing PPE materials could be achieved from layered
fabric systems with electrospun nanofibrous web. 相似文献
7.
A novel approach to preparing multifunctional composite nanofibrous membrane was developed. Polyacrylonitrile (PAN) nanofibrous membrane was fabricated by electrospinning and then the nitrile groups in PAN copolymer was chemically modified to obtain amidoxime modified PAN (AOPAN) nanofiber membrane which was further used as a functional support for laccase immobilization. During the process of reactive dye degradation catalyzed by the AOPAN nanofiber membrane immobilized with laccase, metal ion adsorption occurred at the same time. The chemical modification was confirmed by Fourier transform spectroscopy (FTIR). Scanning electron microscope (SEM) was employed to investigate the surface morphologies of the electrospun nanofibers before and after laccase immobilization. The effects of environmental factors on laccase activity were studied in detail. It was found that the optimum pH and temperature for the activity of immobilized laccase was 3.5 and 50 °C. The relative activity retention of the immobilized laccase decreased dramatically during the initial four repeated uses. After 20 days’ storage, the activity retention of immobilized laccase was still high above 60 %. It has also proved that laccase immobilized on AOPAN nanofiber membrane performed well in dye degradation and metal ion adsorption. 相似文献
8.
An allometrical scaling relationship between the diameter of electrospun nanofiber and solution concentration is established,
the scaling exponent differs greatly between different polymers and the same polymer with different molecules or the same
molecules with different properties. The diameter of electrospun polyacrylonitrile (PAN) nanofibers increases approximately
linearly with solution concentration. 相似文献
9.
Chan-Hee Park Chae-Hwa Kim Leonard D. Tijing Do-Hee Lee Mi-Hwa Yu Hem Raj Pant Yonjig Kim Cheol Sang Kim 《Fibers and Polymers》2012,13(3):339-345
This paper reports on the preparation and characterization of nanofibers and nanofiber/film composites fabricated by electrospinning
and dip-coating. The polymers in this study consist of polyurethane, nylon-6, and silicone. Scanning electron microscopy (SEM),
fiber distribution, X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and tensile tests were
conducted. The electrospun nylon-6 nanofiber/dip-coated silicone film (dried for 5 min) showed the optimum tensile strength
and strain results, showing an increase in tensile strength of 63 % compared to pure nylon-6 nanofiber alone. XRD and FTIR
verified the presence of individual polymers in the composite matrix. The electrospun PU nanofiber produced the biggest fiber
diameter, while electrospun nylon-6, and PU/nylon-6 produced uniform fiber diameters, with PU/nylon-6 obtaining very random
and curved fiber morphology. 相似文献
10.
Atta Akbari Omid Moini Jazani Mohammad Reza Saeb Kobra Pourabdollah Fariba Soltanolkottabi 《Fibers and Polymers》2014,15(6):1230-1235
A proper collector is designed and examined in electrospinning process to produce electrospun nanofibers with favored mechanical propertied. The quality of product was controlled by changing and optimizing the process variables, namely electrospinning time, gap distance, and collector rotating speed in a manner that well-aligned yarns were fabricated from polyacrylonitrile (PAN) dilute solutions. It was found that the tensile characteristics of fabricated yarns are greatly dependent on the process variables. Incorporation of multi-walled carbon nanotubes (MWCNTs) into the polymer solution revealed improvement to the yarn strength because of enhancement in alignment of the filaments. The state of fiber alignment and dispersion of MWCNTs were detected by means of scanning electron microscopy. It was illustrated that combination of nanofibers and microfibers gives PAN/MWCNTs composite nanofibers with high surface area and high porosity to satisfy sophisticated users. 相似文献
11.
Introduced recently, electro centrifuge is a new method for nanofiber production. In the electro-centrifuge method, fibers are produced by the simultaneous use of electrical and centrifugal forces. In this research, the effective parameters in the production of PAN nanofibers diameter and the influence of each of them have been discussed. These parameters are voltage, rotation speed, flow rate of exiting solution from nozzle and viscosity of solution. Also the capability of fiber production by this method is compared with the conventional electrospinning system. Results show that a significant enhancement can be achieved by proper adjustments of the polymer solution viscosity, applied voltage, and rotational velocity in fiber production rate. To exemplify, in a PAN polymer solution, the increased production rate of electro centrifuge varied from 193 to 1200 percent, as compared with a similar electrospinning method in which the polymer concentration and applied voltage varied in a range of 13 to 16 wt% and 15 to 10 kV, respectively. 相似文献
12.
In this study, electrospun wool keratose (WK)/silk fibroin (SF) blend nanofiber was prepared and evaluated as a heavy metal
ion adsorbent which can be used in water purification field. The WK, which was a soluble fraction of oxidized wool keratin
fiber, was blended with SF in formic acid. The electrospinnability was greatly improved with an increase of SF content. The
structure and properties of WK/SF blend nanofibers were investigated by SEM, FTIR, DMTA and tensile test. Among various WK/SF
blend ratios, 50/50 blend nanofiber showed an excellent mechanical property. It might be due to some physical interaction
between SF and WK molecules although FTIR result did not show any evidence of molecular miscibility. As a result of metal
ion adsorption test, WK/SF blend nanofiber mats exhibited high Cu2+ adsorption capacity compared with ordinary wool sliver at pH 8.5. It might be due to large specific surface area of nanofiber
mat as well as numerous functional groups of WK. Consequently, the WK/SF blend nanofiber mats can be a promising candidate
as metal ion adsorption filter. 相似文献
13.
Ibrahim M. Alarifi Waseem S. Khan AKM Samsur Rahman Yulia Kostogorova-Beller Ramazan Asmatulu 《Fibers and Polymers》2016,17(9):1449-1455
This paper reports the fabrication, characterization and simulation of electrospun polyacrylonitrile (PAN) nanofibers into pre-impregnated (prepreg) carbon fiber composites for different industrial applications. The electrospun PAN nanofibers were stabilized in air at 270 °C for one hour and then carbonized at 950 °C in an inert atmosphere (argon) for another hour before placing on the prepreg composites as top layers. The prepreg carbon fibers and carbonized PAN nanofibers were cured together following the prepreg composite curing cycles. Energy dispersive X-ray spectroscopy (EDX) was carried out to investigate the chemical compositions and elemental distribution of the carbonized PAN nanofibers. The EDX results revealed that the carbon weight % of approximately 66 (atomic % 72) was achieved in the PAN-derived carbon nanofibers along with nitrogen and lower amounts of nickel, oxygen and other impurities. Thermomechanical analysis (TMA) exhibited the glass transition regions in the prepreg nanocomposites and the significant dependence of coefficient of thermal expansion on the fiber directions. The highest value of coefficient of thermal expansion was observed in the temperature range of 118-139 °C (7.5×10-8 1/°C) for 0 degree nanocomposite scheme. The highest value of coefficient of thermal expansion was observed in the temperature range of 50-80 °C (37.5×10-6 1/°C) for 90 degree nanocomposite scheme. The test results were simulated using ANSYS software. The test results may be useful for the development of structural health monitoring of various composite materials for aircraft and wind turbine applications. 相似文献
14.
Guangxiu Tian Quan Ji Dongmei Xu Liwen Tan Fengyu Quan Yanzhi Xia 《Fibers and Polymers》2013,14(5):767-771
The study employs limiting oxygen index (LOI) measurements, cone calorimetry (CONE) and thermogravimetric analysis (TGA) to examine the catalytic effect of zinc ion content on the flame retardance and thermal degradation of alginate fibers. LOI results show that all zinc alginate fibers are intrinsically flame retardant, with LOI values of over 27.0, as compared with about 24.5 for alginic acid fiber. The heat release rate (HRR) and total heat release values of zinc alginate fibers (obtained from CONE) are significantly less than those of alginic acid fiber, and decrease with increasing zinc ion content. TGA indicates that char formation increases and maximum thermal weight-loss rate is reduced when zinc content in the fibers is increased. The residues of zinc alginate fibers keep their shapes better than those of the alginic acid fiber. Further discussion of the combustion process and flame retardant mechanism is presented. 相似文献
15.
Electrically conductive nanofibers were fabricated from elastic polyurethane (PU) and PU/multiwalled carbon nanotubes (MWCNTs) nanocomposite by electrospinning method. The nanocomposites were electrospun at various MWCNTs loading. Electron microscopy was used to investigate nanofibers morphology and dispersion of MWCNTs in the electrospun nanofibers. The results showed that the presence of the MWCNTs promoted the creation of fibrous structures in comparison with the PU without MWCNTs. On the other hand, increasing the MWCNTs content resulted in a slight increase in the average fiber diameter. TEM micrographs and mechanical properties of the electrospun mats indicated that the homogeneous dispersion of MWCNTs throughout PU matrix is responsible for the considerable enhancement of mechanical properties of the nanofiber mats. Electrical behavior of the conductive mats was also studied, in view of possible sensor applications. Cyclic experiments were conducted to establish whether the electrical properties were reversible, which is an important requirement for sensor materials. 相似文献
16.
The coating modification of polyacrylonitrile (PAN) fibers with boric acid to enhance the controllability of thermally oxidative
stabilization process. The stabilization process, cross-section morphologies of oxidized and carbonized products were investigated
by means of optical microscopy, SEM, XPS and in-situ thermal shrinkage indicator. The results indicated that the coating with
boric acid on fiber surface was effective to avoid skin-core heterogeneity on the cross section and, in the stabilization
process, that boric acid as a crosslinking agent to tie together the adjacent oxidative molecular chains was confirmed. It
was suggested that the crosslinked structures should play an essential role in controlling the formation of uniform oxidized
structures, which is favorable for tensile properties of carbon fibers. 相似文献
17.
Sung Hee Kim So Yun Jeon Pil J. Yoo Lyong Sun Pu Jun Young Lee 《Fibers and Polymers》2013,14(12):1975-1980
In order to realize flexible organic light emitting diode (OLED), it is critically important to protect moisture and oxygen penetration into the flexible device through the polymer substrates because of intrinsically poor stability of organic materials of OLED to moisture. Since complete protection of the moisture penetration is almost impossible, moisture absorbents are used inside OLED. In this study, metal oxide/polymer hybrid nanofiber with mechanical flexibility and efficient moisture absorption capability was fabricated by electrospinning. Hydrophilic poly(vinyl pyrrolidone) (PVP) or hydrophobic poly(vinylidenefluoride) (PVDF) and calcium oxide (CaO) were used as the fiber forming polymers and as the moisture absorbing particle, respectively. Polymers were first dissolved in appropriate solvents and CaO was then dispersed in the prepared polymer solutions. The hybrid solution was then electrospun, producing the hybrid nanofiber web looking like paper with thickness of about 100 µm. It was observed that all CaO particles were uniformly held by the nanofiber. It was also observed that only a small portion of the surface of CaO particles was covered by fiber since the fiber diameter was much smaller than the CaO particle size. This implied effective moisture absorption through the free surface of CaO. The hybrid nanofiber absorbed moisture very efficiently upto about 70 % of the nanofiber mass. Once moisture was absorbed by the nanofiber, it was never released even at 150 °C in vacuum for 2 hours. It is, therefore, expected that the nanofiber may be applied as the flexible thin moisture absorbent to improve stability of the flexible OLED. 相似文献
18.
Application of electrospun silk fibroin nanofibers as an immobilization support of enzyme 总被引:1,自引:0,他引:1
Ki Hoon Lee Chang Seok Ki Doo Hyun Baek Gyung Don Kang Dae-Woo Ihm Young Hwan Park 《Fibers and Polymers》2005,6(3):181-185
Silk fibroin (SF) nanofibers were prepared by electrospinning and their application as an enzyme immobilization support was
attempted. By varying the concentration of SF dope solution the diameter of SF nanofiber was controlled. The SF nanofiber
web had high capacity of enzyme loading, which reached to 5.6 wt%. The activity of immobilizedα-chymotrypsin (CT) on SF nanofiber was 8 times higher than that on silk fiber and it increased as the fiber diameter decreased.
Sample SF8 (ca. 205 nm fiber diameter) has excellent stability at 25°C by retaining more than 90 % of initial activity after
24 hours, while sample SF11 (ca. 320 nm fiber diameter) shows higher stability in ethanol, retaining more than 45% of initial
activity. The formation of multipoint attachment between enzyme and support might increase the stability of enzyme. From these
results, it is expected that the electrospun SF nanofibers can be used as an excellent support for enzyme immobilization. 相似文献
19.
The concept of phase separation was coupled with electrospinning to induce polyacrylonitrile (PAN) and polystyrene (PS) bicomponent
electrospun fibers that, upon removal of the phase-separated PS domains by solvent extraction, became nanoporous. Electrospinning
of PAN (Mw 150 kDa) with 5 % w/w PS (Mw 250 kDa) at a 10 % w/w total concentration in N,N-dimethylformamide (DMF) produced fibers with stable morphology and average diameters from 1130±680 to 890±340 nm by FESEM.
The nanoporous fibers made from a 95/5 w/w PAN/PS bicomponent precursor had internal pores of about 20∼110 nanometers. Pore
sizes of the porous PAN fibers were decreased to approximately ∼25 nm after oxidation and carbonization thermal treatment
because of fiber shrinkage during the thermal treatment. The fibers retained a high density of pores after the thermal treatment. 相似文献
20.
Electrically conducting nanofibers based on cellulosic materials offer cheap and safe class of materials that can be used for water desalination. In the present work, high conducting cellulose triacetate (CTA) nanofibers containing multiwall carbon nanotubes (MWCNTs) with very low percolation threshold concentration (0.014 wt%) were produced by electrospinning. Unprecedentedly, a hydrophilic ionic liquid consists of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was used to dissolve CTA producing a solution of 10 wt%. This CTA solution was used to engineer both bare CTA nanofibers and CTA nanofibers impregnated with MWCNT. The fabricated nanofibers were characterized by the field emission-scanning electron microscopy (FE-SEM) and the high-resolution transmission electron microscopy (HR-TEM). Both FE-SEM and HR-TEM images showed that the MWCNTs were inserted and uniformly distributed inside electrospun nanofibers. Furthermore, mechanical properties such as tensile strength of MWCNTs loaded-CTA electrospun nanofibers was significantly improved by up to 280 % and 270 % for the Young modulus, when compared with the bare CTA fibers. In addition, the surface properties as the hydrophilicity of electrospun nanofibers membrane was enhanced due to the presence of MWCNTs. Moreover, the electrical conductivity of MWCNT loaded-CTA electrospun nanofibers was greatly enhanced after the implementation of the MWCNTs inside the CTA fiber. The performance of composite nanofiber for water desalination was examined in a lab-scale classic capacitive deionization (CDI) unit, at different concentrations of salt. The obtained data revealed that the electro-adsorption of anions and cations on the surface of MWCNTs loaded-CTA electrospun nanofibers electrodes were monitored with time and their concentration were decreased progressively with time and reaches equilibrium. 相似文献